1. Field of the Invention
The present invention relates to equipment and a method for manufacturing a semiconductor device, and more particularly, to heat treatment equipment for processing a wafer through a heat treatment process and a method of driving the same.
2. Description of Related Art
Generally, semiconductor devices are manufactured by repeatedly performing various processes such as photolithography, diffusion, deposition, etching, metallization, etc. on a semiconductor substrate made of pure silicon.
Of these manufacturing processes, diffusion and deposition processes are performed by a heat treatment process at a high temperature. Heat treatment equipment for performing the heat treatment process can be horizontal heat treatment equipment and/or vertical heat treatment equipment, i.e., vertical furnace equipment. Typically, the veridical heat treatment equipment is mainly used in the semiconductor manufacturing process to meet high productivity and reliability requirements.
The conventional vertical heat treatment equipment includes a process tube which is heated to a high temperature and has an aperture at its bottom surface such that a wafer is transferred into the interior of the vertical heat treatment equipment, a tube cap for sealing the bottom surface having the aperture of the process tube, a motor rotating at a predetermined speed to lift the tube cap by a predetermined distance such that the tube cap seals the bottom surface of the process tube, a gear assembly engaged with the motor, a lifting unit containing a ball screw coupled to the gear assembly, and an encoder controlling a rotation value of the motor such that the lifting unit allows the tube cap to move up to a position suitable for sealing the process tube.
The conventional vertical heat treatment equipment seals the aperture of the process tube.
An operator inputs a value corresponding to a rotation value of the motor to the encoder to rotate the motor.
The motor rotates in response to the input value, and the tube cap is lifted by a predetermined distance by the motor, the gear assembly engaged with the motor, and the ball screw coupled to the gear assembly, thereby sealing the aperture of the process tube.
However, the conventional vertical heat treatment equipment may cause several problems because the operation for sealing the aperture of the process tube is performed by an encoder value input by the operator.
When the aperture of the process tube is sealed by the encoder value input by the operator, an encoder value smaller than a predetermined encoder value which should be input may be input. In this case, the tube cap does not reach a position suitable for sealing the aperture of the process tube, so that a leak may occur. That is, the aperture of the process tube may not be sealed. As a result, internal temperature and pressure of the process tube in which the diffusion or deposition process is being performed may not be appropriate, leading to many processing problems. In order to solve the above described problems, a predetermined encoder value is obtained through many repetitions of testing, and then the process is performed using the obtained encoder value. However, this method may have a problem in that the tube cap may not move to a position suitable for sealing the aperture of the process tube due to, for example, degradation of the gear assembly or the ball screw.
When the aperture of the process tube is sealed by the encoder value input by the operator, an encoder value larger than a predetermined encoder value which should be input may be input. In this case, the motor rotates more than an allowed rotation value due to the larger encoder value. This not only causes excessive impact on the gear assembly engaged with the motor and the ball screw but also may destroy the tube cap which is moved by the gear assembly and the ball screw.